In the past, motors have often been used as a drive source for fans, air ventilators, and various other machines. Generally, a motor is driven by a motor driving apparatus having a full wave rectifier for performing full wave rectification on alternating current voltage from an alternating current power source, and/or an inverter unit for using rectified voltage to generate a drive voltage for driving the motor. However, there have been problems in the motor driving apparatus, such as a decrease in the power factor because of a distortion in the input current from the alternating current power source flowing into the full wave rectifier.
To counter this problem, a rectification device 501 disclosed in Japanese Laid-open Patent Application 2007-274818 is known as a technology for improving the power factor (see FIG. 1). The rectification device 501 is primarily provided with a full wave rectifier 505, two rectification diodes D502, D503, and one switching element 504 constituted of, for example, a transistor. Each of the anode terminals of the rectification diodes D502, D503 is connected to the alternating current input terminals of each of the phases of the full wave rectifier 505, and each of the cathode terminals is connected to a positive electrode of the switching element 504. A negative electrode of the switching element 504 is connected to a negative-side output terminal of the full wave rectifier 505. In such a rectification device 501, the switching element 504 is turned on and off by a microcomputer (not shown) such that the input current flowing into the full wave rectifier 505 becomes a sine wave, and such that the voltage phase and the current phase are in conformity.